1. Field of the Invention
This invention relates to valves for controlling the flow of fluid through a line, and more particularly to valves of the plug type in which inlet and outlet ducts in a valve casing are brought into fluid communication through a port formed in a valve body by rotating the valve body within the casing. Still more particularly it deals with improved means in such valves for adjustably maintaining a fluid-tight seal between the valve body and the inlet and outlet ducts.
2. Prior Art
Fluid valves of the rotary plug-type are well known. The principal problem posed by such valves is the need to maintain a fluid-tight seal between the rotating valve body or plug and the inlet or outlet ducts in the casing wall.
Failure to effectively seal these ducts, and especially the inlet duct, not only prevents the valve from controlling the flow of fluid through the line, but in addition leads to errosion and, if not remedied, eventual destruction of the plug, scoring of the inner wall of the casing, damage to the plug bearing, and fluid leakage.
A variety of means have been devised to overcome this problem. Generally these depend on conventional fluid retaining devices such as rings, packing glands, deformable plugs, and the like. While some of these may be temporarily effective, they are subject to wear, physical and chemical deterioration and fatique, particularly when the fluid with which they are used is abrasive, chemically reactive or extremely hot or cold. Because proper sealing depends on the maintenance of close tolerances between the plug or its seals and the casing wall, the useful life of these prior art valves is more or less limited.
The principal object of the subject invention is to provide a plug valve having sealing means which afford optimal flow control under all operating conditions, and which can be adjusted to compensate for changes in those conditions and for unavoidable wear and deterioration of the valve components.
Another object is the provision of such a valve in which the sealing means can be adjusted while the device is in operation.
Still another object is the provision of a plug valve of this type which requires a minimum of maintenance and which can be maintained and repaired quickly and easily when necessary.
Other objects and advantages of the invention will become apparent from the description which follows.